Knarf1Man
Civil/Environmental
- Oct 17, 2002
- 7
Hi all.
We are designing a new public road and my question is regarding the correct/preferred method for using a "Design-Speed". All vertical & horizontal geometry for the new road will comply with AASHTO & State-DOT standards.
I've read/been-told that the Design-Speed is always higher than the "Posted-Speed". The AASHTO Green-Book doesn't really spell out any "rules-of-thumb" on the subject, only some gobbly-goop about using the 85th percentile of actual vehicle traffic-speeds (lol).
We would like to use a Posted-Speed of 30 mph. Due to existing topo/property constraints, we need to keep the Design-Speed as low as possible. We anticipate a low daily traffic volume under 2000 veh/day.
So ...... is a Design-Speed of 35 MPH ok? Or do we need to bump-it up to 40 MPH.
All comments/suggestions appreciated on this subject.
Thanks-In-Advance.
We are designing a new public road and my question is regarding the correct/preferred method for using a "Design-Speed". All vertical & horizontal geometry for the new road will comply with AASHTO & State-DOT standards.
I've read/been-told that the Design-Speed is always higher than the "Posted-Speed". The AASHTO Green-Book doesn't really spell out any "rules-of-thumb" on the subject, only some gobbly-goop about using the 85th percentile of actual vehicle traffic-speeds (lol).
We would like to use a Posted-Speed of 30 mph. Due to existing topo/property constraints, we need to keep the Design-Speed as low as possible. We anticipate a low daily traffic volume under 2000 veh/day.
So ...... is a Design-Speed of 35 MPH ok? Or do we need to bump-it up to 40 MPH.
All comments/suggestions appreciated on this subject.
Thanks-In-Advance.